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Insulating a vented crawlspace

Posted by betsymcl (My Page) on
Sun, Jul 27, 08 at 10:16


We added on a family room several years ago that has a crawlspace underneath. It has always been cold in the family room in the winter.

The crawlspace is vented with a concrete floor and concrete walls. There is insulation in the floor of the family room already. There are heating ducts which run through the crawlspace which are round, flexible and also insulated, with black plastic (similar material to a heavy duty trashbag) on the outside.

We were wondering if it might be useful to block the vents, and insulate the walls. We're thinking there may not be as much heat loss through the ducts, and also having the crawlspace warmer might keep the room above warmer.

Any thoughts are appreciated!!


Follow-Up Postings:

RE: Insulating a vented crawlspace

Generally speaking, I think you can do that. But if the vents are closed, I believe you would have to lay down a vapor barrier over the concrete also (since it would release moisture that would get trapped in there).

Better wait for other opinions, though.

RE: Insulating a vented crawlspace

What you propose is more common in newer, better-built homes. Check the link below to for the details of how to do a conditioned crawlspace properly.

Here is a link that might be useful: Conditioned Crawlspace

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